The lawlessness of it all shines right through. Thus, until the McDarby case, the conventional wisdom had been that a person with the fewest cardiovascular risk factors would make the best plaintiff. The more risk factors in the mix -- age, gender, cholesterol level, smoking, hypertension, family history -- the harder it would be to finger Vioxx. This is what is known as the "cause in fact" requirement -- if the plaintiff would probably have suffered the same fate with or without the defendant's product, there can be no "abreaction" recovery. But the McDarby's case represented a new approach by Plaintiffs. McDarby was a diabetic who was 75 at the time of his heart attack, atherosclerotic and a former smoker. His lawyers embraced their client's health profile and declared that he was "the last person who should've been on Vioxx." This is an invitation to substitute negligence (by whom? the physician, presumably, as Merck cannot identify all who use its products) for causation.

The fact that someone like Mr. McDarby could get to the jury changes the equation about litigation strategy, lawyers say. That he could prevail is extremely troubling.